Code review comment for lp:~edwin-grubbs/launchpad/bug-526001-edit-packaging-oops

Summary
-------

Fix bug where an exception is raised if you try to change the
productseries for a sourcepackage, when the current productseries
is obsolete.

Implementation details
----------------------

If the current context.productseries is not in the series_list variable,
add it. The code that converts the series_list into SimpleTerm objects
was moved below that if-statement.

Tests
-----

./bin/test -vv -t 'xx-distribution-packages.txt|xx-also-affects-upstream-default-values.txt|sourcepackage-views.txt|xx-sourcepackage-packaging.txt'

Demo and Q/A
------------

* Open https://launchpad.dev/ubuntu/warty/+source/mozilla-firefox/+edit-packaging
    * Set the product series.
* Open the productseries page that you used.
    * Change the status to OBSOLETE.
* Open https://launchpad.dev/ubuntu/warty/+source/mozilla-firefox/+edit-packaging
    * The current project should already be entered, so just click "Continue".
        * The obsolete series should show up as a radio button option
          instead of raising an exception.